In the past decade, the performance-based method has been applied to the seismic evaluation and retrofit of bridges. Suspension bridges are not covered by AASHTO specifications. Therefore, project-specific performance criteria are required. Suspension bridges are mostly critical bridges and generally need to be analyzed for two levels of seismic hazards: function (e.g. 500-year return period); and safety (e.g. 2500-year return period). In addition, the analysis methodology including site-response analysis and soil-structure interaction analysis will generally be required for suspension bridges. Seismic retrofits following the performance-based approach are usually more cost-effective than those derived from the force-based approach.
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